The present invention relates in general to fittings for tubular conduits. In particular, the present invention relates to terminal fittings and couplings for hydraulic systems which utilize tubular conduits to transport fluid.
Prior art couplings and terminal fittings have utilized the familiar worm gear clamp or snap ring clamp to compress a resilient conduit to conform to a separate attachment nipple which is inserted into the central bore of the tubular conduit.
This compression provides a leak-proof seal between the conduit and the nipple.
A prime disadvantage of the simple worm gear clamp or snap ring clamp is that these mechanisms do not protect the terminal end of the conduit from abrasion or cutting. Should the terminal portion of the conduit become cut or abraded, the seal between the attachment nipple and the conduit will fail and the fitting will leak.
In prior art attempts to provide protection for the terminal portion of hydraulic conduits an external housing has been provided. These prior art housings have, in general, been provided with internally threaded portions which enable the coupling to be screwed onto the end of a resilient conduit. The conduit conforms to the internal threads, and self-threads to form a leak-proof seal between the conduit and housing. The separate attachment nipple is then connected directly to the housing.
The principal disadvantages of these prior art attempts to protect the terminal portion of the tubular conduits are first, the seal strength and attachment strength between the conduit and the housing are limited by the shear modulus of deformation of the conduit material with respect to the thread cross-section and pitch. Second, if the use of armored conduit for high pressure applications is desired, it is impractical to use the self-threading method of housing attachment due to the force required to screw on the housing and the non-homogeneous surface contact between the housing and the conduit armor layer which will prevent a leak-proof seal.
It can be readily seen from the foregoing discussion that there is a need for improvement over the prior art solutions to the problems of conduit fittings and attachment methods. A highly desirable improvement would combine a terminal housing to protect the conduit with a mechanism which provided a positive leak-proof attachment between the conduit, the housing and the separate attachment nipple regardless of the materials from which the conduit, housing or nipple were fabricated.